1. Field of the Invention
This invention relates to a method for isolating a relief valve by the use of special equipment which limits the ability of operating personnel to isolate the relief valve unless the special equipment is available.
2. Background
Relief valves are widely used to control pressure build-ups in pressurized vessels, pressurized operating units (herein referred to as vessels) and the like. Such relief valves are typically set to open when a predetermined pressure is exceeded to vent material contained in the vessel to prevent pressures beyond the preset level in the vessel. In some instances, conditions may exist which cause a relief valve to open frequently. In some instances, such valves are not self resetting and operating personnel may be required to climb to the top of a vessel or the like to reset the relief valve. When the relief valve is activated frequently, it is not uncommon for operating personnel to conclude that the relief valve should be closed. If a valve is available in the line from the pressurized vessel to the relief valve the valve may be closed to prevent the frequent trips necessary to reset the relief valve. Such a practice obviously results in a safety risk since the pressurized vessel no longer has a pressure relief. Such practices are discouraged but are occasionally found to have occurred.
Accordingly, a continuing search has been directed to the development of a method for isolating a relief valve which will permit the isolation of the relief valve for maintenance and the like while limiting the ability of operating personnel to isolate the relief valve for other purposes.